View Full Version : running p0171?

12-20-2007, 01:15 PM
i searched and found like a billion threads about p0171 but cant find what im looking for....iv been throwing a p0171 for a really long time(cant find the problem) i was wondering if it was safe to drive around in limp mode? and for how long?....

12-20-2007, 08:42 PM
am i the only one running with the code on?....

12-20-2007, 09:05 PM

That code is Fuel Trim,Bank1 System too Lean

When was the last time you changed your spark plugs and have you checked for any cracked vac lines?

12-21-2007, 12:02 PM
could also be a maf on its way out. try cleaning it as well as what mike said.

12-21-2007, 12:20 PM
i replaced the maf and did a boost leak test from the diy section and still no luck....also did a visual check everywhere possible...couldnt find anything...spark plugs huh? didnt think of that....i bought the car used and never did them ...how do i know if there going bad? or do i just spend the money and cross my fingers?....

12-21-2007, 05:42 PM
I have the same code but it comes on randomly. I was told MAF but haven't changed anything yet. Let me know what works for you

12-22-2007, 08:51 AM
wait, if its running lean wouldnt it be more likely to say its the injectors other then the spark plugs?...like maybe theyre all gunked up?(please correct me if im completely wrong)...

12-22-2007, 10:35 AM
bad plug or poor ignition would typically cause a rich condition.

lean condition would be either not enough fuel (injectors gunked would do it) or the engine thinks there is less air than there is (maf going out)

12-22-2007, 01:38 PM
My light came on again last night, and I popped the hood and was looking at the ignition coils, and I was getting a lot of weird vibration from cylinder 1 and 4, i'm going to change the spark plugs just incase, let you know what happens..

12-22-2007, 02:14 PM
ok well after i was thinking about a gunked up injector i figured i would spend like $6 and buy one of those injector cleaners at autozone poured it in and cleared the code...drove ab out 50 miles today and no cel...im just waiting to see if this helps the problem...if not then im goin to try the spark plugs then coils...

12-23-2007, 01:06 PM
ok well as i was driving today my friend the cel came back...so im guessing its not the injectors....im gunna try and run down to an autozone probably wensday cuz everythings closed till then and pick up some new spark plugs...thinking about going with the BKR6E's any one have any problems with them?...i live in ny so i get both hot and cold climates...so im hoping ill be able to keep these in all year round...if the plugs dont do it i dont know where to go next?...any suggestions?...

01-02-2008, 08:42 PM
ok so heres an update...i picked up new spark plugs on wed...installed them and everything was fine untill today....CEL CAME BACK!!! ugh im getting sick of this thing...so now my next idea is the coil packs..is this correct? also i was wondering...could they be going bad and not missfire?...im still getting a p0171 but cant find the problem...also on a side note...when i installed the new spark plugs i found some oil on the plug closest to the car cabin...could this be the cause of my problem or is it just a gasket?...and could that be my problem?...

01-02-2008, 10:47 PM
log you MAF reading. there's a how to on ross-tech's website

01-03-2008, 01:04 AM
well i kept getting the code and then my igniton coil died on me, coincidence maybe but I just bought new coils, spark plugs, fuel filter, etc from ecs so we'll see if I have the problem after I install everything

01-03-2008, 01:17 PM
i just installed new spark plugs and new maf so i guess coils are next...havnt thought of fuel filter tho...i might have to order from ecs now...let me know if it works out for u...

01-04-2008, 02:50 PM
ok somebodys gotta have another idea...just did the fuel filter this morning and now the cels back again...its really pissin me off...so far iv done maf, dv, pressure test, spark plugs, fuel filter and nothings worked for longer then a day...i did check the spark plugs again and found some more oil on the threads but only on the one closest to the back of the car...im thinking valve cover gasket but i doubt thats making me throw a code...PLEASE HELP ME! im completely out of ideas...

01-04-2008, 04:11 PM
Another thing that can cause lean conditions is a bad o2 sensor that still allows a signal to be sent to the ecu. I don't know about vag logs but on the equipment at work I can watch the voltage output of the first o2 sensor as I step on the gas to see if the increase and decease of voltage coinsides with rpm and pedal position.

01-05-2008, 08:08 AM
is there any way for me to check the o2 sensor? or do i have to go out and jus buy one and cross my fingers?...

01-05-2008, 09:57 AM
When the exhaust gasses exit the vehicle they exit in wave form so if you have or have access to equipment showing the voltage output you can see if the signal appears to be strong or weak. I work on Toyota's with Toyota equipment, I don't have vag com and haven't had much experience with Audi's but there are certain voltage parameters I can look up in the tech. information system to tell whether the voltage is within specs but only on Toyota's. Normally it is visible because instead of the voltage fluctuating it is more of a steady voltage like the voltage output from the post catalyst o2. I have seen it quite a few times where the 02 has had a low signal output causing a lean condition with no cel because the heater circuit in the o2 sensor is still working and the sensor is still giving a signal. On Toyota's the o2 sensor will throw either a bank 1 lean code or a long term fuel trim code or both.

01-05-2008, 02:15 PM
would that also cause me to go into limp mode for about a day before it throws a cel? i reset the cel but i havnt been able to boost past 5psi(limp) but i know that cel will light up within a couple hours...i can feel it...

01-05-2008, 04:58 PM
I have yet to have my code come back on, I haven't installed my fuel pump yet but I have a feeling its my maf. I ran some logs and the readings are way too low. I go back to school tomorrow and i'm not taking my car so I'm not going to worry about getting a new maf yet but let me know if the o2 sensor solves your problem incase I run into the same thing..

01-05-2008, 05:06 PM
ok def...but before i go out and buy a new o2...is there a way to tell if its the pre-cat or post-cat? or do i go out and buy one then if it doesn't solve the problem go out and buy the other one?...anyone one know how?...maybe a way to tell visually?...

02-25-2008, 12:08 PM
I have had the same problem with that reading. First time I the car started to run very rough the stalled. When I restarted it ran ok then the cel came on. I appnt with dealer to replace the fuel pump (recall) and they found the a bad coil so I had them replace all 4 ($500). The light stayed on so they said it may be the 02 Sensor. Again wanted $500 ( the mechanic there said it was ok to drive and save my money) I bought a Vag Cam on ebay and now clear it when it comes on , lasts about 2 weeks

02-25-2008, 12:24 PM
ok def...but before i go out and buy a new o2...is there a way to tell if its the pre-cat or post-cat? or do i go out and buy one then if it doesn't solve the problem go out and buy the other one?...anyone one know how?...maybe a way to tell visually?...

the pre cat o2 sensor is the only one that has to do with fueling. the post cat is the one that makes sure your cat is doing its job [up]

02-25-2008, 12:43 PM
yep gotaudi your right, i replaced the pre cat o2 and cleared the cel and now the cars perfect...been good for about a month now...

02-26-2008, 12:21 PM
HOw much did it cost you to replace the o2 sensor Annon and did you do it your self?

02-26-2008, 12:45 PM
cost me like $75 i think and yes its really easy to do...i got it from here: http://www.autopartswarehouse.com/search/?D=audi+a4+oxygen+sensor&Ntt=audi+a4+oxygen+sensor&Dx=mode+matchall&Ntk=Main&Ntx=mode+matchallpartial&N=4294967266&Nty=1

02-26-2008, 05:05 PM
Thanks for that information, You know the dealer wanted to charge $250 for parts and $250 for labor.

03-23-2008, 10:06 PM
i ran a p0171 and had it vagcommed.. the maf was giving off inconsistent readings, so i orderd a new one from worldimpex inc for like 110 and it fixed everything.. i bought the car with the CEL on and I guess it was in "safe" mode, because now with the new MAF and no CEL it drives like a whole new car... i was happy with the performance before, but now im very happy

03-23-2008, 10:28 PM
I would change the plugs if you dont know when they have been changed last anyways. The longer they are in there the harder it will be to get them out without f'in something up.

03-24-2008, 01:46 PM
Not sure if you ever fixed the problem but..

I had the same code for awhile and then got the "long term" code eventually

I replaced the MAF - still there
replaced several vacuum lines - still there
replaced the vac line from under the manifold that runs to the DV- problem fixed! The old line appeared to be ok but once I had it out i wiggled it around a bit and it was all crunchy / dried out. CEL hasn't been back since.

I also bought new O2 sensors but didn't install them, still in the garage.


03-25-2008, 12:28 PM
Fighting this code too, cleaned maf, found one vac leak, new plugs and coilpacks and still p0171, guess I have to got me eBay cable working to get some maf logs.

03-25-2008, 01:39 PM
I have this code also. I bought a new o2 sensor, but the place sent the wrong one so I'm going to attempt to return it for my money back. In a few weeks when it warms up enough, I'll replace all my vacuum lines and hope for the best. I've got relatively low miles for an 01, only 60k.. so I thinking it's something other than my MAF or o2 sensor.

The code usually only shows up when I'm on the highway accelerating at 70mph. I'm not in limp mode though as I've heard some people saying.. just bogs down a little right before the CEL shows up. Otherwise the car runs fun with the code, haven't really noticed a loss in mpg or power.. just the bogging down for a few seconds before the CEL shows up.